With ever-increasing demands on automated, computer-controlled driving and braking, and at the same time an ever-decreasing available structural space, negative-pressure brake force boosters, which are of large construction, reach their technical limits. It is therefore known to use brake devices with electromechanically driven hydraulic booster stages.
Such booster stages must ensure reliable functioning both in an externally actuated or fully autonomous, driver-independent actuation mode and in a manual, driver-initiated actuation mode, and also on a fall-back level in the event of malfunctions of the booster stage or a failed energy supply.
At the same time, there is the desire to optionally use the hydraulic booster stage instead of a negative-pressure brake force booster utilizing the same mechanical interfaces, and to obtain haptic feedback or pedal feel similar to that obtained with the negative-pressure brake force booster.
Known generic brake devices are normally of complex construction with electrically switchable valve devices for implementing different actuation modes. To ensure that the brake pedal is driven along in an autonomous actuation situation, it is likewise the case in known brake devices that cumbersome technical solutions are necessary.
Known brake devices with hydraulic booster stages which use heavy and expensive high-pressure accumulators as a pressure source are considered to have particular potential for improvement owing to the increased weight, structural space expenditure and switching effort.